South Korea added 25 new coronavirus cases Sunday, marking the third consecutive day the number has been around 20, as the country steps up efforts to bring the latest infections tied to Seoul's nightlife district of Itaewon under control.

The 25 new cases, with eight coming from overseas and 17 being local infections, raised the country's total caseload to 11,190. The death toll remained unchanged at 266, the Korea Centers for Disease Control and Prevention (KCDC) said in a statement.

The Itaewon-linked confirmed cases reached a total of 225 as of 12:00 p.m. Sunday, the statement said.

Of the new cases, six each were reported in Seoul, its surrounding Gyeonggi Province and North Gyeongsang Province, with two infections reported in Incheon, just west of Seoul, and one in Gangwon Province. Four cases were caught during the quarantine process at airports, it said.

The accumulated number of people released from quarantine after making full recoveries stood at 10,213, up 19 from a day earlier, with 711 people under quarantine, the statement said.

South Korea has successfully flattened the virus curve with massive and swift testing since the country's first confirmed case was reported on Jan. 20, but sporadic cluster infections continue to complicate the KCDC's quarantine efforts.

Cases tied to clubs in Itaewon have not evolved into explosive infections but have continued to increase steadily.

But the health authorities are still on high alert ahead of an expanded school reopening this week as COVID-19 still continues to spread across the country.

The KCDC sees the next two weeks as a significant watershed to determine whether the coronavirus outbreak spreads further or slows down as the government plans to push ahead with another round of school reopenings this week despite concerns over possible virus transmissions at schools.

High school seniors returned to school last week.

Itaewon emerged as the latest hotbed for infections after a 29-year-old man tested positive for COVID-19 on May 6 following visits to clubs and bars in the district. The country has continued to report secondary to quintic transmissions linked to the Itaewon outbreak in recent weeks.

To avoid a second wave of infections, the health authorities have been carrying out tens of thousands of tests on those who visited affected clubs between April 24 and May 6.

The pandemic, which surfaced in China late last year, has killed more than 340,000 people worldwide and infected more than 5.3 million in just a few months, a tally from Johns Hopkins University showed. (Yonhap)